Papers by Keyword: Size Control

Abstract: A series of well dispersed ruthenium nano-clusters using Polyvinylpyrrolidone (PVP) as stabilizer were synthesized by seed-mediated method. In this method, polymer-stabilized PVP-Ru nano-cluster with a diameter of about 3.14 nm was prepared by the reduction of RuCl3 in ethylene glycol and used as a seed solution (S), which was then added to the EG solution of ruthenium (Ⅲ) salts (E) to control the size of the Ru nano-cluster synthesized in this seed-mediated method. The influences of the amount of S solution that was added to E solution and the existence of PVP in ruthenium salts solution on the size of Ru were studied in this essay. Compared with the seed solution, the size of Ru nano-cluster increased with the decreasing of the amount of seed solution added. Moreover, the existence of PVP in the EG solution of ruthenium salts would hinder the Ru nano-cluster from growing since PVP will weaken the ability for newly formed Ru0 to regrow on the seed crystal.

Abstract: In this work, monodispersed silver nanoparticles with controllable size have been successfully in situ synthesized in PMMA matrix. NaHS, HCl and poly (vinyl pyrrolidone) (PVP) were used to optimize the nucleation and growth of silver nanocrystalline. UV–vis analysis and transmission electron microscopy (TEM) were used to characterize the size and dispersion of silver nanoparticles in the Ag/PMMA nanocomposites. The results show that silver nanoparticles homogeneously distribute in PMMA/DMF sol and the particle size of silver nanoparticles increase with the increasing of time. The nucleation of Ag atoms can be facilitated through the addition of a trace amount of NaHS to generate Ag₂S clusters as heterogeneous nuclei. Introducing a trace amount of Cl^- into the reaction system can effectively reduce the growth rate of the nanoparticles and thus generating more uniform silver nanoparticles in PMMA matrix.

Abstract: WO₃ particles with different grain sizes were prepared by a thermal evaporation method. The composition, morphology, and optical properties of the samples were analyzed by powder X-ray diffraction, scanning electron microscopy, and UV–vis absorption and photoluminescence spectroscopy. Their photocatalytic properties were evaluated by decomposing methylene blue in aqueous phase. It was found that the smaller the grain size of the prepared WO₃ particles, the better the degradation effect on methylene blue.

Abstract: Porous Al with controlled pore size was prepared by the spacer method including spark plasma sintering and the dissolution of space-holding NaCl particles. The NaCl of the controlled pore size (particle diameter control range of 5˰ڌm~20˰ڌm) were prepared by precipitation method. The effects of sintering condition such as the sintering electric current intensity, voltage and the size, morphology and content of NaCl powder on the porosity and size of porous Al are investigated. The porous Al with higher porosity of 69.41% and smaller pore size of 5 ڌm was obtained.

Abstract: We reported a facile synthesis route for size controlled preparation of gold nanoparticles (Au NPs) by controlling concentration of the reducing agent and temperature. Nearly monodisperse Au NPs with mean diameters of 2-6 nm are acquired via the reduction of HAuCl₄ by NaBH₄ in the presence of tri-n-octyl amine and dodecanethiol in solvent of toluene. Results indicate that concentration of the reducing agent and temperature are key factors to tune the particle size and uniformity in the synthesis of Au NPs. The as-synthesized Au NPs show size dependent surface plasmonic properties between 510 and 525 nm, while Au NPs with size smaller than 3 nm do not clearly show the property.

Abstract: Gripper with two claws of automatic placing and removing manipulator is designed in this paper, and structure characteristics, working theory and positional error analysis are introduced. This gripper has the function of automatic center aligning and size control. The chucking size of gripper can be modified automatically in order to be adaptable when clamping different work pieces and this gripper, which could shorten the time and improve the efficiency, is designed to place and remove workpiece at one time beat. The gripper has a virtue of better ability to locate and move, improving the precision of automatic feeding manipulator and lathe cutting. The grippers have the advantages of simple structure, small volume and weight, which can solve the problems of complicated structure and massive volume for typical translational gripper. They also could simplify the control system of manipulator; meet the demand of placing and removing workpiece instead of complicated and heavy manual work.

Abstract: Fe3O4 particles were prepared by the co-precipitating method in the presence of polyethylene glycol (PEG). They were characterized by the Transmittance electron microscopy (TEM) and Fourier transform infrared (FT-IR) spectroscope, which indicate the formation of spherical Fe3O4 particles with a wide range of sizes (up to 200 nm in radius) and the polydispersity of particle size below 20%. Furthermore, the magnetic properties of Fe3O4 particles were measured using a vibrating sample magnetometer (VSM), indicating that the particles possess high saturation magnetization at room temperature. These results are attributed that the Fe3O4 particles were directly coated with PEG in a seeded growth Sto¨ber process.

Abstract: The size of quantum dots (QDs), their shape, and ordered arrays have significant impact on electrical and optical properties of the QDs. We synthesized near-infrared-emitting PbSe QDs via an oil phase method in a noncoordinating solvent. Transmission electron microscopy (TEM) and photoluminescence (PL) spectroscopy were used to characterize the samples. Sizes of the QDs were accurately controlled from 4.2 nm to 10.2 nm through control of the reaction time as well as the growth temperature. The PL spectra showed strong size dependence, which is large red shift with increasing size of the QDs.

Abstract: X-ray irradiation was applied to control the size of metal colloids in a silicate glass to make a high precise photosensitive glass containing K2O, Na2O, ZnO BaO, 0.01-0.05wt.% Au metal as sensitizer, <1.2wt.% Sb2O3 and SnO2 as thermal reducer. Colorimetry showed that X-ray irradiation effectively works to make the color of red system. Transmission electron microscopy revealed that the metal colloids were oxided and had uniform and spherical shape of 10-20 nm. Au colloid made various colors like pink after heating at 400°C, red at 500°C and dark-red at 600°C. Ag colloid made them like yellow-green at 400°C, yellow at 500°C and dark-brown, respectively.

Abstract: An easy onepot reaction for the synthesis of iron oxide nanoparticles is reported. Thermal decomposition of iron acetyl acetonate (Fe(acac)3) in diphenyl ether, in the presence of oleic acid and oleyl amine followed by calcination, leads to the formation of iron oxide nanoparticles. Variation of concentration of the oleyl amine during the synthesis affects the morphology of the iron oxide nanoparticles produced.